Catalytic dehydroisomerization of five membered alicyclic ring hydrocarbons having six or more carbon atoms per molecule to aromatic hydrocarbons



Patented 1.... 21, 1941 Robert A. Trimble, El Cerrito, Calif., assignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application August 22, 1944,

. Serial No. 550,674

12 Claims.

This invention relates to the production of aromatic hydrocarbons and relates more particularly to the direct dehydroisomerization of five membered alicyclic ring compounds having at least six carbon atoms to the molecule to aromatic hydrocarbons. A particular aspect of the invention relates to the dehydroaromatization of methylcyclopentane to benzene.

Petroleum is becoming of increasing importance as a source of highly desirable aromatic hydrocarbons. Processes proposed heretofore, for the production of aromatic hydrocarbons from petroleum include many directed to the separation of aromatic hydrocarbons originally present therein by such procedures as fractional distillation, solvent extraction, extractive distillation, etc.

cycloparafilns of hydroaromatic structure such as, for example, the dehydrogenation of cyclohexane to benzene.

Many of these processes, although nomically unfeasible. Others arerendered unattractive by relatively low yields. These processes often even dependent upon, hydrocarbon production step bons. Cyclohexane, for lytically dehydrogenated example, has been catato benzene. Such processes, however, do not enable the utilization of five membered alicyclic aromatic hydrocarbons, rality of separate reactions. is converted to benzene by successive steps involving, first, the isomerization of the methylcyclopentane to cyclohexane and thereafter, the separate dehydrogenation of the cyclohexane formed to benzene. Such a plurality of steps is often sufficiently costly and complex to render their practical application, as well as the execution of other processes carried out in conjunction therewith, highly impractical.

In accordance with the present invention the five membered alicyclie ring compounds having at least six carbon atoms to the molecule are converted to aromatic hydrocarbons in a single step operation. Methylcyclopentane is converted directly to benzene. The reaction mechanism involved, resulting in the direct, single step conversion of a cyclic hydrocarbon containing a fivemembered alicyclic ring to a hydrocarbon containing a six-membered ring of aromatic character, is termed throughout the specification and appended claims dehydroisomerization.

It has been found recently that the dehydroisomerization reaction is promoted by certain highly specific catalysts. Of the many dehydrogenation catalysts such as chromium oxide, tungsten oxide, vanadium oxide, titanium oxide, iron oxide, platinum, nickel, etc., the only catalyst so far found enabling the execution of the reaction with relatively favorable yields is molybdenum oxide. Tungsten sulfide and molybdenum sulfide are found to exert to some degree a favorable effect upon the dehydroisomerization reaction. These sulfide catalysts have the"highly advantageous attribute of being immune to poisoning by sulfur and the sulfur-containing materials often present as impurities charge. The catalytic effect of. the tungsten sulfide or molybdenum sulfide upon the dehydroisomerization reaction is, however, so slight as to render the production of aromatic hydrocarbons from cyclic hydrocarbons containing a five membered alicyclic ring with the aid of these catalysts highly impractical.

It has now been found that the catalytic effect of tungsten sulfide and molybdenum sulfide upon the dehydroisomerization reaction is markedly influenced by the presence of nickel. It has furthermore been found that the presence of nickel in the tungsten or molybdenum sulfide within well defined concentrations enables the eflicient direct dehydroisomerization of five membered alicyclic ring compounds having at least six carbon atoms to the molecule to aromatic hydrocarbons with high yields,

The catalysts comprising tungsten sulfide, or molybdenum sulfide, and a promotional amount of nickel are prepared in any of many suitable ways. vention contain the nickel in the freshly prepared catalyst in the sulfided state. Particularly preferred catalysts comprise those prepared under conditions involving the precipitation of nickel in the sulfide form in the presence of sulfur compounds of tungsten or molybdenum. A preferred method of preparing the promoted catalysts of the invention is as follows:

To an ammonium thiotungstate solution, prepared from an ammoniacal aqueous tungstic acid solution with hydrogen sulfide, there is added an aqueous solution of nickel nitrate. A precipitate consisting largely of nickel sulfide forms. Dilute sulfuric acid is added until the hydrogen ion concentration of the resulting mixture, in terms of the pH values, is in the range of from about 1 to about 2. Tungsten is thereby precipitated as tungsten trisulfide. The precipitate is separated from the liquor by filtration and/or centrifuging. The resulting tungsten-nickel sulfides are dried and calcined at a temperature of from about 400 to about 425 C. in. a hydrogen atmosphere, thereby effecting the conversion of tungsten trisulfide to tungsten disulfide.

The catalyst is employed as such in the form of lumps, pills, extrudates, or in any other suitable shape or form assuring efficient contact between catalyst and reactants during use. The catalyst may furthermore be deposited upon, or diluted with, suitable solid support material comprising, for example, porous adsorptive materials such-as carbon, Activated Alumina, bauxite, adsorptive clays, magnesia, etc.

As stated above, the degree of catalytic effect upon the dehydroisomerization reaction is dependent upon the concentration of nickel in the catalyst. It has been found that superior catalysts resulting in the attainment of more efficient operation with high yields of the desired aromatic hydrocarbon comprise those having a nickel content in the range of from about 2% to about and preferably from about 4% to about 11% by weight of the total metal content of the catalyst. Though the utilization of catalysts containing in the hydrocarbon Preferred promoted catalysts of the insomewhat greater or lesser amounts of nickel is contemplated within the scope of the invention such catalysts are, however, not generally preferred because their lesser catalytic eifect upon the dehydroisomerization reaction generally renders impractical their utilization in large scale operation. Catalysts of unusual activity with respect to the dehydroisomerization reaction are those having a nickel content of about 7%. By the term total metal content of the catalyst as used throughout the specification and claims is meant the summation of the total ultimate content of tungsten and/0r molybdenum and nickel in the catalyst regardless of the manner or proportion in which any or all of these metals are combined with other chemical elements such as, for example, sulfur, in the catalyst. Determination of the nickel concentration within the prescribed range necessary to attain a catalyst of desired dehydroisomerization activity is therefore not only independent of the elements chemically combined with the metal content of the catalyst but is also independent of the composition or amount of solid support or diluent material added to the catalyst either during or after its manufacture.

In accordance with the process of the invention the five membered alicyclic compounds having at least six carbon atoms to the molecule are contacted in the vapor phase with the catalyst in any suitable type of reactor enabling efilcient contact of the catalyst with the hydrocarbon charge. Such reactors may utilize the catalyst in the form of stationary or moving beds or even in a suspended or fluidized state. Five membered alicyclic ring compounds having at least six carbon atoms to the molecule which are capable of undergoing conversion to aromatic hydrocarbons in accordance with the invention include the hydrocarbons containing a pentacarbocyclic ring of saturated or unsaturated character in which at least one of the hydrogen atoms attached to a carbon atom in the ring is replaced by an alkyl or alkenyl group. Such five membered alicyclic ring compounds comprise cyclopentane and cyclopentene in which at least one of the hydrogen atoms is replaced by an alkyl or alkenyl group, for example, methylcyclopentane, ethylcyciopentane, propylcyclopentane, isopropylcyclopentane, dimethylcyclopentane, trimethylcyclopentane, tetramethylcyclopentane, l-methyl-2-ethylcyclopentane, diethylcyclopentane, methylene cyclopentane, cyclopentylacetylene, 1-methyl-2- isopropenyl cyclopentane, 1-methyl-2-isopropylidene-cyclopentane, 3-methyl-1-methylene-cyclopentane,- ethylidene-cyclopentane, 1-methyl-2 ethylidene cyclopenetane, 1,1,2-trimethyl 3- methylene cyclopentane, l-methyl-l-cyclopentene, 3-methyl-l-cyclopentene, 1,2-dimethyl-lcyclopentene, 3,3 -dimethyl-1-cyclopentene, lethyl-l-cyclopentene, l-isopropyl 1 cyclopentene, 1,2,3-trimethyl-l-cyclopentene, 1,3 dimethyl-2-ethyl-l-cyclopentene, l-vinyl-l-cyclopentene, l-propenyl-l-cyclopentene, 1-methyl-2- isopropenyl-l-cyclopentene, etc. The hydrocarbon charge to the reaction zone may consist of essentially only one five membered alicyclic ring compound having at least sixcarbon atoms to the molecule or may comprise more than one such cyclic hydrocarbon capable of direct dehydroisomerization to aromatic hydrocarbons. The hydrocarbon charge may furthermore contain other hydrocarbons capable or not of undergoing conversion under conditions of execution of the dehydroisomerization reaction. Suitable hydrocarbon charge material comprises hydrocarbon mixtures of relatively narrow boiling range containing at least one five membered alicyclic compound having at least six carbon atoms to the molecule, such as are obtained by fractionation, solvent extraction, extractive distillation. etc., 01' readily available hydrocarbon mixtures containing the cyclic hydrocarbons. A particularly desirable charge comprises a concentrate oi the five membered alicyclic compound having at least six carbon atoms to the molecule such as, for example, a methylcyclopentane concentrate, obtained by fractionation of hydrocarbon mixtures such as naphthenic straight run gasolines or other suitable methylcyclopentane-containing hydrocarbon mixtures.

The hydrocarbon charge is contacted with the catalyst under dehydroisomerizing conditions. Suitable dehydroisomerizing conditions include, for example, a temperature in the range of from about 400 to about 600 C. and preferably in the range of from about 475 to about 525 C. The reaction is executed under superatmospheric pressure, for example, in the range of from about 5 to about 100 atmospheres.

of from about 1 atmosphere to about 100 atmospheres and preferably from about 5 to about 45. Hydrogen is introduced into the reaction zone in admixture with the hydrocarbon charge or may be separately introduced in part, or in its entirety, at one or several points along the length of the reaction zone. Sulfur, or sulfur-containing compounds, present in the reactants exert a favorable influence upon the catalyst life. Small amounts of sulfur, for example, in the form of hydrogen sulfide, are therefore preferably added to the hydrocarbon charge or to the hydrogen passed to the reaction zone. In a preferred method of carrying out th process, sulfur present in the reaction products, for example, in the form of hydrogen sulfide, is recycled, at least in part, together with the hydrogen to the reaction zone. The contact time is maintained within a range of, for example, from about 4 seconds to about 500 seconds.

Under the above-defined conditions five membered alicyclic ring compounds having at least six carbon atoms to the molecule are converted efiiciently in a singl step operation to aromatic hydrocarbons. Thus, methylcyclopentane is converted to benzene with high yields andin the absence of any substantial amount of undesirable side reactions. Regeneration of the catalyst is effected by burning off deposited carbonaceous material with the aid of oxygen or oxygen containing gases in the usual manner. Excessive amounts Of sulfur removed in this operation are replaced by treatment of the catalyst in situ with hydrogen sulfide.

The following examples are illustrative of the efiiciency with which five membered alicyclic ring compounds having at least six carbon atoms to the molecule are dehydroisomerized to aromatic hydrocarbons in a single step operation in accordance with the invention.

EXAMPLE I Methylcyclopentane was contacted under dehydroisomerizing conditions with a catalyst con-' sisting of unpromoted tungsten sulfide. In three further separate operations methylcyclopentane was contacted under the same dehydroisomerizing conditions with catalysts consisting of precipitated mixtures of tungsten sulfide and nickel sulfide prepared as above. The nickel content of each of the catalysts in percent by weight. and the benzene content in percent by volume in the reaction product of each in Table A. The dehydroisomerizing conditions used in each of the runs were as'follows:

Temperature 490 C. Pressure 20 atm. Contact time secs. Moi ratio of added hydrogen to feed 3.0

Table A M ig gzi Benzene in Run Catalyst weight of total i g metalcontentol y catalyst 1.. Tungsten sulfide 0 9 2 Tungsten sulfide-nickel 6.05 45 sulfide. do..... 7.05 81 do 13.75 19 EXAMPLE II Methylcyclopentane was contacted under the dehydroisomerizing conditions of Example I with a catalyst consisting of unpromoted molybdenum sulfide. In a separate operation under identical dehydroisomerizing conditions methylcyclopentane was contacted with a catalyst consisting of molybdenum sulfide and nickel sulfide having a nickel content of 8.3% by weight based on the total metal content of the catalyst. The benzene content of the product obtained with the unpromoted molybdenum sulfide catalyst was only 8 percent by volume whereas the benzene content of the product obtained with the molybdenum sulfide-nickel sulfide catalyst amounted to 34 percent by volume.

I claim as my invention:

1. A process for the direct conversion of methylcyclopentane to benzene which comprises contacting methylcyclopentane under dehydroisomerizing, conditions with a catalyst comprising a member of the group consisting of tungsten sulfide and molydbenum sulfide containing about 7 per in the sulfided state.

2. A process for the direct conversion of methylcyclopentane to benzene which comprises contacting methylcyclopentane under dehydroisomerizing conditions with a catalyst comprising a member of the group consisting of tungsten sulfide and molybdenum sulfide containing a promoting amount of nickel in the range of from about 4 to about 11 per cent by weight of the total metal content of the promoted catalyst, said nickel being in the sulfided state.

3. A process for the production of benzene from a mixture of hydrocarbons containing methylcyclopentane which comprises contacting said hydrocarbon mixture under dehydroisomerizing conditions with a catalyst comprising a member of the group consisting of tungsten sulfide and molybdenum sulfide containing a promoting amount of nickel in the range of from about 2 to about 15 percent by weight of the total metal content of the promotedcatalyst, said nickel being in the sulfided state, thereby effecting the dehydroisomerization of methylcyclopentane to benzene.

4. A process for the direct conversion of methylcyclopentane to benzene which comprises contacting methylcyclopentane under dehydroisomerizing conditions with a catalyst consisting essentially of tungsten sulfide containing about 7 per cent by weight or nickel based upon the total metal content of said catalyst, said nickel being in the sulfided state.

5. A process for the production of benzene from a mixture of hydrocarbons containing methylcyclopentane which comprises contacting said hydrocarbon mixture under dehydroisomerizing conditions with a catalyst consisting essentially of tungsten sulfide containing a promoting amount of nickel in the range of from about 2 to about percent by weight of the total metal content of the promoted catalyst, said nickel being in the sulfided state, thereby effecting the direct conversion or methylcyclopentane to benzene.

6. A process for the production of benzene from a mixture of hydrocarbons containing methylcyclopentane which comprises contacting said hydrocarbon mixture under dehydroisomerizlng conditions with a catalyst consisting essentially of molybdenum sulfide containing a promoting amount of nickel in the range of from about 2 to about 15 percent by weight of the total metal content of the promoted catalyst, said nickel being in the sulfided state, thereby effecting the direct conversion of methylcyclopentane to benzene.

"I. A process for the direct conversion of cycloparaffins of non-hydroaromatic structure having at least six carbon atoms in the molecule and containing five carbon atoms in the ring to aromatic hydrocarbons which comprises contacting said cycloparafiins of nonhydroaromatic structure under dehydroisomerizing conditions with a catalyst comprising a member of the group consisting of tungsten sulfide and molybdenum sulfide containing about '7 per cent by weight of nickel based on the total metal content of said catalyst, said nickel being in the sulfided state, thereby effecting the direct conversion of cycloparaflins of nonhydroaromatic structure to' aromatic hydrocarbons.

8. A process for the direct conversion of five membered alicyclic .ing compounds having at least six carbon toms to the molecule to aromatic hydrocarbons which comprises contacting said five membered alicyclic ring compounds under dehydroisomerizing conditions with a catalyst comprising a member of the group consisting of tungsten sulfide and molybdenum sulfide containing a promoting amount of nickel in the range of from about 4 to about 11 per cent by weight of the total metal content or the .promoted catalyst, said nickel being in the sulfided state, thereby effecting the direct conversion of said five membered alicyclic ring compounds to aromatic hydrocarbons.

9. A process for the production of aromatic hydrocarbons from a hydrocarbon mixture containing five membered alicyclic ring compounds having at least six carbon atoms to the molecule which comprises contacting said hydrocarbon mixture under dehydroisomerizing conditions with a catalyst comprising a member of the roup consisting of tungsten sulfide and molybdenum sulfide containing a promoting amount of nickel in the range of from about 2 to about 15 percent by weight of the total metal content of the promoted catalyst. said nickel being in the sulfided state, thereby effecting the direct conversion of said five membered alicyclic ring compounds to aromatic hydrocarbons.

' 10. Aprocess for the direct conversion of cycloparaflins of nonhydroaromatic structure having at least six carbon atoms in the molecule and containing five carbon atoms in the ring to aromatic hydrocarbons which comprises contacting said cycloparaflins of nonhydroaromatic structure under dehydroisomerizing conditions with a catalyst consisting essentially of tungsten sulfide containing a promoting amount of nickel in the range of from about 4 to about 11 per cent by weight of the total metal content of the promoted catalyst, said nickel being in the sulfided state.

11. A process for the production of aromatic hydrocarbons from a hydrocarbon mixture containing five membered alicyclic ring compounds having at least six carbon atoms to the molecule which comprises contacting said hydrocarbon mixture under dehydroisomerizing conditions with a catalyst consisting essentially of tungsten sulfide containing a promoting amount of nickel in the range of from about 2 to about 15 percent by weight of the total metal content 'of the promoted catalyst, said nickel being in the sulfided state, thereby effecting the dehydroisomerization of said five membered alicyclic ring compounds to aromatic hydrocarbons.

12. A process for the production of aromatic hydrocarbons from a mixture of hydrocarbons containing five membered alicyclic ring compounds having at least six carbon atoms tothe molecule which comprises contacting said hydrocarbon mixture under dehydroisomerizing conditions with a catalyst consisting essentially of molybdenum sulfide containing a promoting amount of nickel in the range of from about 2 to about 15 percent by weight of the total metal content of the promoted catalyst, said nickel being'in the sulfided state, thereby effecting the dehydroisomerization of said five membered alicyclic ring compounds to aromatic hydrocarbons.

ROBERT A. TRIMBLE. 

